In recent years, endoscopes have widely been used for examination in medical and industrial fields. An electronic endoscope having an image pick-up device is recently used.
A video processor is used for the electronic endoscope as a signal processing apparatus for performing signal processing of the image signal which is picked up by the image pick-up device.
FIG. 24 shows a conventional electronic endoscope apparatus 61. The electronic endoscope apparatus 61 comprises an electronic endoscope 62, a video processor 63 connected to the electronic endoscope 62, and a monitor 64 for displaying a video signal outputted from the video processor 63.
The video processor 63 comprises a floating circuit 70 which is further insulated from a secondary circuit at a portion connected to the image pick-up device incorporated in the electronic endoscope 62.
The floating circuit 70 comprises a drive circuit 71 for driving the image pick-up device, a pre-process circuit 72 for amplifying the image signal which is photoelectrically converted by the image pick-up device by applying a drive signal from the drive circuit 71, and an A/D converting circuit 73 for converting an output signal as an analog signal from the pre-process circuit 72 into a digital signal.
The digital signal converted by the A/D converting circuit 73 is inputted to a white balance circuit (abbreviated to a W/B) 74 forming a part of a secondary circuit 83 via an insulating circuit such as a photocoupler (not shown). The secondary circuit 83 corresponds to a part other than the floating circuit 70 in the video processor 63.
After adjusting the white balance by the white balance circuit 74, the signal is inputted to an automatic gain control circuit (AGC circuit) 75. An amplitude of the signal is amplified to a predetermined level and thereafter the signal is inputted to a gamma circuit (abbreviated to a γ circuit) 76. After γ correction, the signal is inputted and is temporarily written to a field memory 77.
The signal written to the field memory 77 is read at a predetermined timing, and is converted into the analog signal by a D/A converting circuit 78. Then, the signal is inputted to a post process circuit 79, is subjected to processing for converting the signal into the video signal, becomes the video signal, and is outputted to the monitor 64 from an output terminal.
The video processor 63 comprises a PLL circuit 81 for generating a signal synchronous with a reference clock to generate a reference signal, and a synchronous signal generating circuit (abbreviated to an SSG) 82 for generating horizontal and vertical synchronous signals synchronously with the PLL circuit 81. An output signal from the synchronous signal generating circuit 82 is applied to a circuit necessary for the synchronous signal, thereby performing processing synchronously with the synchronous signal.
The secondary circuit has a large-scaled FPGA (field programmable gate array) circuit formed by recent device technologies. In the circuit scale forming the conventional function, a device occupying area on a substrate is reduced. The circuit scale is formed by substantially single substrate.
However, in the case of adding a new function and another-TV-system signal processing circuit, the circuit scale is increased and it cannot be formed by the single substrate. Then, it is considered that the number of substrates including the entire functions is plural in the first step of the development. However, this is not advantageous in views of development costs and products.
Facilities using the electronic endoscope apparatus are varied and functions required for the facilities are also varied. One user needs the emphasis of pathology which is performed by visualizing invisible information using an image processing function, a support diagnosis function, high resolution, high picture quality, and the like. Another user needs only a necessary observation function and the like with a low price. It is desired that the electronic endoscope apparatus corresponding to wide users are to be sold.
The present invention is devised in consideration of the above circumstances. It is an object of the present invention to provide an electronic endoscope apparatus and a signal processing apparatus which can correspond to the requests of wide users with low costs.